Arc welding apparatus



Jur-e 8 1965 F. E. ADAMsoN ETA'L 3,188,375

ARC WELDING APPARATUS 2 Smeets-Shree?l 1 Filed Aug. 13, 1962v INVENTORS Floyd E. Adamson on Roger R Gler @L ATTORNEY June 8,1965 F E ADAMSON ETAL 3,188,375

ARC WELDING APPARATUS Filed Aug. 13, 1962 2. Sheets-Sheet 2 25., ...A m U United States Patent O 3,188,375 ARC WELDING APPARATUS Floyd E. Adamson, Eggertsville, N SY., and Roger R.

Giler, Canonsburg, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 13, 1962, Ser. No. 216,689 3 Claims. (Cl. 219-131) This invention relates to arc welding and has particular relationship to are welding in which the welds are of limited measured duration such as in arc-spot welding.

In such industries as the automotive industry it has been the practice in the past to fabricate such structures as automobile bodies by resistance spot or seam welding. Recently the resistance welding has been replaced by arc welding; in particular arc-spot welding has been used for burn-through or lap-tack welds. Where arc welding can be used the large and cumbersome press resistance Welders and their controls may be dispensed with and the fabrication carried out at a substantially lower capital outlay than by resistance welding. In addition, the arc welding apparatus is highly portable and has greater liexible than resistance welding. Another factor is that the arc-welding current demands are substantially lower than the resistance-Welding current and a saving in power is effected and disturbances of power lines presents no serious problem.

Arc-spot welding is semi-automatic. The operator controls neither the speed of the electrode over the distance nor the distance of the electrode from the joint being welded. The operator places a nozzle particularly suited to the joint being welded as taught by Morley Patent 2,845,524 over .the joint and presses the trigger on a gun andthe weld is produced. The speed of the electrode is determined by the preset speed of the motor which drives the electrode. The distance of the electrode from the work is determined by the rate at which the electrode advances into the are.

A difficulty which has been encountered in using arcspot welding apparatus in accordance with the teachings Iof the prior art in the automotive industry has resulted from the demands that such arc-welding apparatus be ,repeatedly reset for the different thicknesses of materials and for the different materials which are repeatedly encountered in the automotive industry. In some cases, the operator need only interrupt a welding operation and reset a nearby control before continuing. In others, the

resetting may require that the operator climb out of an automobile body to readjust equipment before continuing the welding.

Attempts have been made to meet this difficulty by providing different equipments which are set differently to correspond to the different materials. This requires that the operator lay down one gun and pick up another as the different conditions are encountered. This expedient has the disadvantage not only that it is costly but it also introduces the problem of properly identifying the different guns so that an operator will not use the wrong gun to make a weld .and thus require the work to be scrapped or to be repaired at substantial cost.

It is an object of this invention to eliminate the above described difficulties. Another object of this invention is to provide arc-welding apparatus which shall lend itself to the welding of different materials using a single unit.

In its broader aspects this invention comprehends arc- Welding apparatus including provisions for presetting the welding parameters at different settings and facilities which enable the operato-r to set the apparatus readily at certain of the presettings in dependence upon the demands of the material being welded. While in the interest of simplicity in switching, the apparatus in accordance with this inven- 3,188,375 Patented June 8, 1955 tion usually includes facilities for selecting only a few, usually two or three presettings, the range over which the few presettings can be made should be wide enough to accommodate the wide range of materials encountered. The principal parameters which are variable from one arcspot welding operation to another are the duration of the weld, the speed of the electrode, which determines the welding current, and the welding voltage. It has been found in arriving at this invention that the materials to be welded are so different in the properties affecting the arc welding and particularly in thickness, that the welding apparatus in accordance with this invention must have a wide range of welding capability and to achieve this range at least two and sometimes all three of the above parameters must be variable. In accordance with a specific aspect of this invention, apparatus is provided which includes facilities for presetting both the duration of the weld and the welding current or electrode speed and for selecting one or another of several set-s of these preset parameters in dependence upon the material being welded. It has been found that with apparatus having this welding facility welds over a range meeting the demands of the automotive industry can be met. In accordance with a further speciiic aspect of this invention, the range of the apparatus is further extended by providing facilities for presetting not only the duration and the welding current, but also the potential of the power supplied for welding.

In carrying out this invention, the duration of the welding is preset by presetting the timing of a timer, the timing of which may be carried out by pneumatic means or by means of a controlling valve and the welding current is preset by varying the speed of the motor which drives the electrodes. Specifically, where a valve is used for timing, the conduction of the Valve may be determined by the time of discharge of a capacitor and discharge circuit for the capacitor includes a plurality of selectable discharge components preset to provide different discharge times. The motor speed may be controlled in different ways by means of valves or variable resistors. Typically the motor circuit includes a valve which controls the conduction of current through the motor and the valve includes a control circuit having a plurality of elements which determine the conduction of the valve and by the setting of which the conduction may be preset at different magnitudes. l

The novel features considered characteristic of this invention are described generally above. For a better understanding of this invention, both as to its organization and as to its method of operation, together with additional objects and advantages thereof, referenceis made to the following description of a specific embodiment taken in connection with the accompanying drawings, in which:

FIGURES 1A and 1B together constitute a schematic of a preferred embodiment of this invention.

The apparatus shown in FIGS. 1A and 1B includes a Power Supply Unit for supplyingy power for arc welding work W with an electrode E, an Electrode Drive Unit for advancing the electrode E into welding relationship with the work W, a Control Unit for controlling the advance of the electrode and the cooperation of the Electrode Drive Unit and the Power Supply Unit and a Selector Unit for selecting different sets of welding parameters. The above described division of the apparatus is functional rather than structural. The different Units need not be in separate containers. They may be mounted most conveniently for the use and the operation of the equipment.

The apparatus disclosed may be supplied from the usual commercial supply. The Power Supply Unit is supplied from the commercial buses of a three-phase supply through conductors L1, L2 and L3 whichare rcompensation potential.

energized through the usual circuit breakers or disconnects (not shown). The Control Unit, Electrode Drive Unit and Selector Unit are supplied from conductors ALI and ALZ which supply single-phase alternating current and may be energized from two of the conductors LI, L2 and L3 through a. transformer (not shown) or may be connected independently to alternating current conductors of a commercial power supply. The apparatus shown in FIGS. lA and 1B may be set for manual (MAN), automatic (AUTO) or spot (SPOT) welding by the setting of a switch SW. Since the invention here disclosed involves primarily spot welding the switch SW will be regarded as set for SPOT welding in the description of the apparatus shown in FIGS. 1A and 1B.

The PowerSupply Unit may be of the type disclosed in Bichsel Patent 2,786,160. This Power Supply Unit is ofthe constant-potential type and its output potential is determined bythe setting variable transformers labeled 61, 63, 65 in FIG.1 of the patent. In apparatus in accordance with this invention, the Power Supply Unit includes variable transformers 6IA, 63A, 65A each of which has a plurality of'taps 9IA and @IB which may be preset and selected in one position SIA or the other 921B by operation of contacts MIa, MIb, MIC of a contactor MI controlled from the Selector Unit. When the contacter MI is deenergized, the contacts are in one position providing for one potential for welding. When the contactor is energized, a second potential is provided for welding. The contacter MI is actuable on the closing of contact CRIg in the Selector Unit. The setting of the contactor MI and the selection of the potential supplied for arc welding by the Power Supply Unit is coordinated with a corresponding setting for the electrode speed and the timing by the relay CRI.

The Power Supply Unit includes output terminals or conductors 201 and 203, ZtlI being grounded and d3 being connected to the electrode E through the coil of a current relay SCR. The work W is usually grounded. The relay 3CR has front contacts SCRa and lCRb.

The Electrode Drive Unit is of the type disclosed in Bichsel et aLfPatent 2,913,653 and includes a motor M having an armature A and a shunt eld SF. The shunt lield is energized from conductors ALI and ALZ through rectifier RX. The Electrode Drive Unit also includes a valve which may be a thyratron ITU. This thyratron has an anode 261, a cathode 263 and a grid or control electrode 265.

During normal welding, the armature A is energized in a circuit extending from conductor ALI through the anode 261 and cathode 263 of the thyratron, front contact 2CRa of starting relay ZCR in the Control Unit, the armature A, a resistor R13 which provides a potential for IR drop compensation, contact 267 of the switch SW, front contact ZCRc of the starting relay ZCR to ALZ.

The speed of the motor is determined by the conduction of thyratron ITU and this is set by a control circuit energized from the transformer TI. Transformer TI has a primary TIP supplied from conductors ALI and ALZ-and secondaries TISI, TISZ and TISS. Secondary TISI provides phase-shifted alternating potential in the control circ-uit which is superimposed on a plurality of direct-current component potentials including a selected bias, the potential across the armature A Vand the IR drop This phase-shifted potential is derived froma phase-shift network including a resistor R7 and a capacitor 3C. The phase-shifted potential across the network is set by a variable resistor P3. The

control electrode is connected to the adjusting Varm of the resistor P3 through a-grid resistor R8. The bias for the thyratron ITU is provided by a capacitor C which' quired.

l operation, resistor R3 may be shunted by switch SWS and for low speed operation resistor R4 may be shunted.

Resistors IP and ZP may be selectively connected in the bias circuit in dependence upon the setting of the relay CRI. With :the relay CRI in the unactuated condition, resistor IP is connected in the bias circuit through back contacts CRI]L and back contact CRIc. With the relay CRI actuated, resistor 2P is connected in the bias circuit through front contacts CRIe and CRIa'. The resisters IP and 2P may be preset in accordance with the different speeds of the electrode E desired for different ranges of materials being welded. The setting of the resistors IP and 2P is coordinated with the corresponding settings of the variable transformers 6IA, 63A and 65A. The biasing network including capacitor C is connected to one terminal of variable resistorV P3 of the phase shift network through the junction of the adjustable arms of resistors IP and 2P.

The control circuit also includes a network for irnpressing an IR drop compensation potential dependent on the load current conducted by the armature A through resistor RIS. This potential is impressed on the capacitor 5C which is shunted by resistor RI?J through rectitier ZRT/I. The capacitor 5C is charged from resistor RIS which conducts the armature current so that the charging potential is proportional to the armature current and is a measure of the IR drop compensation re- The control circuit of the Electrode Drive Unit is effective during the intervals during which the thyratron ITU is not conducting and resistor R13 is not carrying current. This control circuit extends from the gridV 265, through the grid resistor RS, the variable resistor P3, the selected variable resistor IP or 2P and the biasing network including capacitor C, the IR drop compensation network including capacitor SC, the resistor R13, the armature A, the front contact ZCRa of the relay ZCR to the cathode 263 of the thyratron. The conduction of thyratron ITU and the speed of the motor M is dependent on the setting of the variable capacitor IP or 2P and the IR drop voltage. By setting the speed of the electrode,

. the arc welding current may be set.

At the start of the welding operation, the electrode is inched towards the work by the Electrode Drive Unit. During inching, the speed of the motor is controlled by variable resistor Pri in a circuit extending from the grid 265 through the resistor R3, the Variable resistor P3, the variable resistor Pd, thev back contact ZTDIa of relay ZTDI, back contact f-tCRa, front contact ZCRc, contact 267 of switch SW, resistor lRIS, armature A, front contact fCRa to the cathode of thyratron 263. y

The Control Unit includes the starting relay SCR having only a front contact ECRa which is actuated by the closing of push button or foot switch SWS to start a welding operation. l The coil of SCR is supplied from the secondary TZS of the transformer T2 energized from the conductors, ALI and AL2. v

The Control Unit also includes the inching relay ICR which is energized from conductors ALI and ALZ through the inch switch SW2 usually on the welding gun (not shown) when this switch is closed. The relay 4CR has in addition to the contact eCRa, contacts dCRb, ftCRc and ICRLL The Control Unit also includes the control relay ICR for the Power Supply Unit. This relay has a front contact ICRcz; when ICRa isclosed, the Power Supply Unit is energized and there is power between conductors ZtlI and 2h35. The coil of relay ICR is adapted to be connected in an energizing circuit supplied from conductors ALI and ALZ which extends from ALI through the coil, back contact oCRa of a test relay, back contact ITDa of a timer ITD, back contact dCRd, a water` pressure switch PWS which is closed when the water pressure is adequate, front contact SCRa to AL2. When SCR isv actuated, the relay ICR is actuated and the Power Supply Unit is energized.

The Control Unit also includes the test relay GCR which is adapted to be energized from conductors ALI and AL2 when test switch SW3 is closed. This relay has in addition to the contact 6CRa, front contact 6CRb and GCRC.

The Control Unit also includes the timer ITD which serves to control the burn-back of the electrode E at the end of a weld. This relay has back contacts ITDa and ITDb and is energized from conductors ALI and AL2. The timing out of relay ITD is started on the closing of Contact 2TDa of relay 2TD. The relationship between timer ITD and relay 2TD is shown in detail in Adamson Patent 3,013,144. Relay GCR of Adamson 3,013,144 corresponds to the relay 2TD of this application. When the relay ITD times out, contact ITDa opens and relay ICR is deenergized, deenergizing the Power Supply Unit, This .occurs after the electrode has burned back to the desired distance at the end of a spot welding operation.

The Control Unit also includes a second timer system which times the duration of the spot weld. This timer includes in addition to the relay ZTD the thyratron VI and the relay ZTDI. The thyratron V1 times the weld duration; relay ZTDI is actuated at the beginning of the timing operation and the relay 2TD at the end of the timing operation. The relay 2TD includes in addition to the contact ZTDa, back contact 2TDb. The relay ZTDI includes the contacts ZTDIa, 2TDIb, 2TDIc, ZTDId and ZTDIe.

The thyratron V1 includes an anode 281, a cathode 283 and a control electrode or grid 285. The coil of the relay 2TD is adapted to be energized in a circuit extending from conductor ALI through the coil, the anode 281, the cathode 283, the front contact SCRa, the pressure switch PWS, the contact SCRa to the conductor AL2. The thyratron V1 is maintained normally non-conducting by the charge on a capacitor 4C in its control circuit. This capacitor 4C is charged through rectifier SRX in a circuit extending from ALI through the rectiier SRX, a resistor 3R, the contact 2TDIb, a capacitor 4C to AL2. At the start of the timing interval, the relay 2TDI is actuated interrupting the charging and the capacitor 4C is discharged through resistor DRI or resistor RDZ in a time interval depending on the setting of the Selector Unit. The discharge circuit for DRI extends from capacitor 4C through contact 2TDIc, front contacts, back contact CRIb and the resistor DRI. When relay CRI of the Selector Unit is actuated, 4C is discharged through CRIa and DRZ. l

They contacty 2DId is not ordinarily used for arc spot welding. It is intended for use when the principal'selector switch is in the AUTO position for fully automatic welding. In arc spot welds such las automotive body work, the gun is portable and the work is stationary with no relative movement while the arc is burning.

The contact'ZTDId when it is used connects the Travel Carriage Control which advances the work W in a circuit extending from conductor ALI through the Travel Carriage Control, the contact 287 of switch SW, contact ZTDId, contact 289 of switch SW, the water pressure switch PWS and contact SCRa. The Travel Carriage Control is also connected in a circuit extending from conductor ALI through the Control, the contact 287, the contact ZTDIe, the contact ITDb to AL2. Situations are anticipated in which the travel carriage will be used in the practice of this invention to produce a plurality or series of spot welds or a plurality of seam welds in different materials.

The coil of relay 2TDI is adapted to be energized in a circuit extending from conductor ALI through the coil, the front contact 3CRa, the pressure switch PWS, the contact SCRa to AL2. This coil has a lock-in circuit extending from ALI through the coil, the switch contact 287, the contact ZTDId, the contact 289, the pressure switch PWS, the contact SCRa to AL2 and also through ZTDIe, ITDb to AL2.

The Control Unit also includes the starting relay ZCR and the water and gas valve solenoids VW and VG. The starting relay ZCR has the contacts ZCRa, 2CRb and 2CRc. The coil of the starting relay and the solenoids VW and VG are supplied in parallel in a circuit extending from ALI to the coils and solenoids, the back contact 2TDIb, the pressure switch PWS, the front Contact SCRa t0 AL2.

The Selector Unit includes the transformer T4 having the primary T4P and the secondary T4S, the relay CRI and the selector switch S1. The relay CRI has the front contacts CREla, CRld, CRIe, CRlg and the back contacts CRIb, CRIc and CRI. With the selector switch S1 open, the back contacts set the weld timer V1, the motor speed and the potential impressed between the electrode E and the work W at one set of magnitudes. With the switch SI closed, the front contacts of the relay CRI are closed and set the weld time, the motor speed, and the welding voltage at a second set of magnitudes. The servo sets of magnitudes may be set to correspond to widely differing materials. In fact for most purposes it is only necessary to provide for selection of one of two weld times and speed control magnitudes. Considering, for example, parts of the same material, but of two different thicknesses, the thinner material would require a lower duration and a lower speed which would result in lower welding current and a lower arc supply voltage. The thicker material would require longer duration, a higher speed resulting in a higher welding current and a higher welding voltage. To the extent that variation within any set of magnitudes may be demanded, such variation may be achieved by varying the settings of the discharge resistors DRI or DR2 in the timing system, the variable resistors IP or 2P in the motor control circuits and the variable transformers 61A, 63A, 65A in the Power Supply Unit.

In the standby condition of the apparatus shown in FIGS. 1A and IB, the switch SWS is open, relay SCR deenergized, relay ICR is then deenergized and the Power Supply Unit is deenergized so that there is no potential between the electrode E and the work W and relays SCR is deenergized. Timer ITD is deenergized, relays ZTD and ECR are deenergized, thyratron VI is non-conducting, relay ZTDI is deenergized. The switch S1 is in the open position and relay CRI is deenergized. With relay ZCR deenergized the motor M is deenergized and the braking resistor R1@ shunts the armature A. Thyratron ITU is deenergized.

Preparatory to a welding operation DRI and DR2 and IP and 2P and if necessary 91A and 91B are set for the proper welding of two of the materials to be welded. Initially S1 may remain open and arc material may be welded and then Sl may be closed and the other material welded.

Initially, then CRI is in the setting shown in the drawings. Each spot welding operation is started by the closing of the switch SWS energizing relay SCR. It the water pressure is adequate, relay ZCR and the solenoids for the valves VW and VG are energized and the gun (not shown) is supplied with cooling water and gas ilows through the gun to pre-purge the material being welded. In addition, relay ICR is energized to energize the Power Supply Unit; potential now appears between the electrode E and the work W.

When relay ZCR is actuated, the anode circuit for the thyratron ITU is closed through contacts 2CRa, 267 and 2-CRc. In addition, the braking resistor R10 is disconnected from the armature A at contact ZCRa. Control potential is now impressed on the thyratron ITU through the variable resistor P4 which sets the thyratron current to correspond to inching speed. This control potential is impressed through the contact ZTDIa, 4CRa, ECRC, 267 and 2CRa. The electrode E now approaches the work W at an inching speed. When the electrode E contacts the work W, the relay SCR is actuated and contact .iCRa closes. The anode circuit through VI is now closed conditioning this thyratron to start timing out. In

alsaers u addition, relay ZTD is actuated and locked in at ZTDTd and fTDle.

The lock-in circuit through ZTDTd is in series with the front contact dCRa and the water pressure switch PWS and includes ZTDb and ETDId. This lock-in contact opens on the opening of the switch SWS. But the second lock-in circuit through TTD!) and ZTDT@ remains closed until llTD times out. This lock-in circuit assures that once start switch SWS is closed the operation continues throughout a complete welding cycie. The charging of the timing capacitor dC is then interrupted at open contact ZTDib.V Capacitor 4C discharges through the resistor DRl and thus the weld time times out. in addition, the circuit through the Travel Carriage Control is closed and locked in at contact ZTDIdand ZTDie. At 2TDIa, the variable resistor Pd is disconnected from the control circuit of the thyratron ITU and the control circuit including resistor lP becomes effective.

The engagement of the electrode E with the work W causes an arc to be fired. The arc now burns and the electrode E is supplied at a speed determined by the variable resistor 1P. This speed determines the welding current. The welding voltage is determined by the setting of the variable transformer 61A, 63A and 65A.

This operation continues until the capacitor 4C is discharged through the resistor DRL The thyratron V1 then lires energizing the relay ZTD. The timing out of TTD is then started at contact ZTDa. After ZTD is actuated, ZTDI remains energized through liTDb and the lock-in contact ZTDIe. The Carriage also continues to advance because of the lock-in contact ZTDIe. The relay lCR remains energized because it is supplied with power through the contacts CRa, lTDa, dCRd, PWS, and SCRa.

The relay ECR is deenergized at Contact ZTDb. With the relay ECR deenergized, the motor circuit is opened and the braking resistor R is connected across the armature A. The motor M then stops. The arc continues to burn so long as contact lTDa remains closed. This time interval is determined by timer ITD which is set to pro duce the desired burn-back. Ultimately relay llTD times out and contacts iTDb and lTDa open. The Travel Carriage control is then stopped, relay ZTDI is then reset and thyratron V1 is deenergized. The required number of welds are completed by repeating the above described operation. Thereafter switch Sl is closed and anothe material is welded.

The apparatus disclosed in FIGS. 1A and 1B enabled the operator without resetting therapparatus to weld two different materials with one apparatus which is preset to correspond to each of the materials. Because facilities for presetting the duration of the weld, the welding current and the welding voltage are provided, the range over which the materials may differ is wide. mous saving ink operators time is eiected with the apparatus.

While a preferred embodiment has been disclosed herein many modifications thereof are feasible. ln its specitic aspects, this invention is applicable to and is peculiarly suitable for, arc welding as distinct arc-melting. To the extent that this invention is applicable to arc-melting, the

i. Arc-welding apparatus for welding workvwith a consumable electrode comprising means connected to said electrode for advancing said electrode into welding relationship with said work, power-supply means connected to said electrode and work for maintaining a welding arc between said electrode and work, timing means connected to said power-supply means for timing the duration of said welding arc, and selective means connected to said advancing means and to said timing means for setting said advancing means to advance said 'electrode at a selected one of a plurality of speeds and simultaneously setting said timing means to a corresponding one o a plurality of durations.

2. Arc-welding apparatus for welding work with a con sumable electrode comprising a motor connected to said electrode for advancing said electrode into welding relationship with said work, an energizing circuit for said motor including controllable valve means -for controlling the supply of current to said motor, power supply means connected to said electrode and work for impressing a potential to maintain a welding arc between said electrodeand work, timing means connected to said power-supply means for timing the duration of said arc, and selective means connected to said valve means and to said timing means for selecting any one of a plurality of preset control settings of said valve means to set the current supplied to said motor at a corresponding magnitude, and simultaneously setting said timing means to a corresponding one of a plurality of preset durations.

3. Arc-welding apparatus yfor welding workv/ith a consumable electrode comprising a motor-*connected to said v t electrode for advancing said electrode into welding relationship with said worlr, an energizing circuit for said motor including'a controllable valve means for controlling the supply of current to said motor, power supply .means connected to said electrode and work for impressing a potential to maintain a welding arc between said electrode and work, timing means connected to saidpower-supply means for timing the duration of said arc, and kselective work.

References Cited hy the Examiner" UNITED STATES PATENTS 2,786,160 3/57 Bichsel 3l5-14l 2,913,653 11/*59' Bichsel 3l8--331 RICHARD M.` WOOD, Primary Examiner. 

1. ARC-WELDING APPARATUS FOR WELDING WORK WITH A CONSUMABLE ELECTRODE COMPRISING MEANS CONNECTED TO SAID ELECTRODE FOR ADVANCING SAID ELECTRODE INTO WELDING RELATIONSHIP WITH SAID WORK, POWER-SUPPLY MEANS CONNECTED TO SAID ELECTRODE AND WORK FOR MAINTAINING A WELDING ARC BETWEEN SAID ELECTRODE AND WORK, TIMING MEANS CONNECTED TO SAID POWER-SUPPLY MEANS FOR TIMING THE DURATION OF SAID WELDING ARC, AND SELECTIVE MEANS CONNECTED TO SAID ADVANCING MEANS AND TO SAID TIMING MEANS FOR SETTING SAID ADVANCING MEANS TO ADVANCE SAID ELECTRODE AT A SELECTED ONE OF A PLURALITY OF SPEEDS AND SIMULTANEOUSLY SETTING SAID TIMING MEANS TO A CORRESPONDING ONE OF A PLURALITY OF DURATIONS. 